The invention relates to a circuit arrangement for transferring energy.
In order to electrically insulate two circuits from one another, it is known to couple the two circuits via a transformer. In this case, an energy transfer takes place in AC operation. If an energy source only provides a DC voltage, an inverter circuit must be provided on the primary side, which inverter circuit converts the DC voltage into AC voltage. Correspondingly, it is necessary to convert the AC voltage into a DC voltage on the secondary side if the consumer is to be driven using DC voltage. The provision of the transformer and the possibly necessary converter devices is associated with a high demand on installation space. Alternatively, electrical insulation between two circuits can be achieved by a primary-clocked switched-mode power supply with a so-called isolating transformer. This also requires a relatively large installation space.
The two variants require a high complexity in terms of circuitry, as a result of which an expensive demand on space is required. Likewise, a high weight results from the known designs. Another disadvantage consists in that the energy transfer in both cases is frequency-limited.
The problem addressed by the present invention is to provide a circuit arrangement for transferring energy, which is structurally and/or functionally improved, with the result that it requires a comparatively smaller installation space.
This problem is solved by a circuit arrangement for transferring energy comprising an energy source, a control device and at least one energy distribution system. Each energy distribution system comprises a basic element and at least one load element. The basic element comprises the first intermediate circuit element which is electrically connectable to or disconnectable from the energy source via the first pair of controllable switch elements, controlled by the control device to form a first energy circuit. The at least one load element comprises a consumer which is electrically connectable to or disconnectable from the connections of the first intermediate circuit energy storage element via the second pair of controllable switch elements, controlled by the control device to form a second energy circuit. The control device is designed to actuate the first and second switch elements of the respective energy distribution system such that energy is transferred from the energy source to the energy consumer or vice versa, wherein at no time is there a direct conducting connection between the energy source and the energy consumer.
As a result of this, it is possible to optionally convert voltage or current between the energy source and the consumer. The control device ensures that the two energy circuits and thus the energy producer and the energy consumer are galvanically separated at all times. The energy transfer is in this system based on one or—as will become apparent from the following description—a plurality of intermediate circuit energy storage elements which are not transformers in accordance to this invention. One advantage of the circuit arrangement consists in that it has a lower weight and a reduced demand on space in comparison with a transformer or a primary-clocked switched-mode power supply. In particular, the circuit arrangement can be produced at a low installation height and a small space. Cost advantages result from this. Furthermore, the circuit arrangement can also be operated at high switching frequencies. A transformer is usually limited to about 200 kHz. The proposed arrangement can be operated at frequencies in the upper megahertz range.
According to the configuration, one or more energy distribution systems can have at least one intermediate element which is or are connected between the basic element and the at least one load element. Each intermediate element comprises a second intermediate circuit energy storage element, wherein each second intermediate circuit energy storage element is electrically connectable to or disconnectable from the two connections of the respectively preceding first or second intermediate circuit energy storage element or the respectively subsequent second intermediate circuit energy storage element or the at least one energy consumer via a pair of controllable switch elements, which are controlled by the control device to form a respective second energy circuit. As a result of this, a chain of energy circuits can be formed between the energy source and the consumer, along which the energy packets can be transported in an electrically isolated manner from the energy source and the consumer.
In a specific implementation, two or more intermediate elements can be connected in parallel with the basic element or a preceding intermediate element. It is alternatively or additionally possible to connect two or more load elements in parallel with the basic element or with one of the intermediate elements. The provision of at least one intermediate element has the advantage, compared to the direct connection of the load element to the basic element, that the consumer of a load element can be continuously supplied with energy.
Furthermore, by providing one or more intermediate elements, any energy distribution network can be formed, and so a plurality of consumers can be supplied with energy from the energy source.
The energy source can be designed as a current source or voltage source, as desired.
In another expedient configuration, a switch element can be connected in parallel with the first intermediate energy storage element, if this is implemented as an inductance. If intermediate elements are present, it is also possible for a respective switch element to be connected in parallel with at least one of the second intermediate circuit energy storage elements. Voltage peaks are reduced and the energy balance is optimized owing to the switch element, appropriately controlled, in parallel to the energy storage elements.
Another variant of the circuit arrangement provides that at least two energy distribution systems are connected in parallel with the energy source. By way of example, the voltages and/or currents provided in the energy distribution systems for supplying different consumers can be of different levels.
When multiple energy distribution systems are connected in parallel, it is expedient for the first intermediate circuit energy storage elements of the basic element of the at least two energy distribution systems to be electrically connected to the energy source at different times. One advantage consists in that the energy source can be evenly loaded as a result of this. If energy is fed into a first energy distribution system at a particular instant, the respective basic element of the further energy distribution system or systems isolates the electrical connection to the energy source. If the first energy distribution system is then isolated from the energy source, with the result that the energy packet stored in the basic element can be transported to the next energy circuit, the next energy distribution system (that is to say the basic element thereof) is then connected to the energy source, etc.
According to another expedient configuration, the control device is designed to switch the connection between the energy source and the energy consumer by selective actuation of the pair of switches of the basic element, the optional intermediate element and the load element to be conducting and blocking such that, at any given instant, at least one of the pairs of switches is blocking As a result of this, the electrical insulation between the energy source and the consumer is ensured at all times. The electrical insulation is thus enabled solely by the controllable switch elements.
In another configuration, the control device is designed to switch the connection between the energy source and the energy consumer by selective actuation of the pair of switches of the basic element, the optional intermediate element and the load element to be conducting and blocking such that an energy packet is transferrable from the energy source via the first intermediate circuit storage element and the optional second intermediate circuit storage element or storage elements to the energy consumer, or vice versa. As a result of this, despite electrical insulation between the energy source and the consumer, the supply of energy to the consumer is ensured.
According to another configuration, the direction of the energy transport between the energy circuits can be reversed as desired by dynamic matching of the actuation of the pair of switches of the basic element, the optional intermediate element and the load element by the control device. This is important, for example, when using the circuit arrangement in a vehicle if the consumer is able to be operated in an energy-recovery mode. The energy obtained in this case can then—by appropriate actuation of the respective pair of switches—be transferred from the load element via one or more optional intermediate element or elements and via the basic element to the energy source, for example a rechargeable battery, which is then an energy sink in this mode.
According to another configuration, the first intermediate circuit energy storage element and/or the at least one second optional intermediate circuit energy storage element of a respective intermediate element comprise, in each case, at least of one inductance and/or a capacitor, as a result of which, with appropriate actuation of the switch elements, each intermediate circuit energy storage element of the following energy circuit can be charged and discharged in sequence until the energy consumer is supplied with energy. This principle can also be used in the opposite direction, as explained.
The load element can include at least one energy storage element in addition to the energy consumer. If the load element, as in its basic form, has only one energy consumer, then the consumer can also be supplied with energy intermittently. In contrast, by way of the energy storage element in the load element, it is possible to continuously supply the energy consumer with energy.
In a variant, the energy storage element of the load element can be an inductance which is connected in series with the consumer, wherein the series circuit composed of the energy storage element inductance and the consumer is connected in parallel with a fourth switch element. In another variant, the energy storage element of the load element can be a charge store which is connected in parallel with the consumer.
The energy storage element can also be formed from a combination of one or more inductances and one or more capacitors.
If the controllable switch elements of the preceding energy circuit (either of the basic element or of an intermediate element) are closed, then the energy contained in the associated intermediate circuit energy storage element can be output to the energy storage element of the load element. The consumer is then supplied from the energy storage element.
According to another configuration, the first and the second pairs of switch elements are semiconductor switch elements. In particular, they are MOSFETs (metal-oxide-semiconductor field-effect transistor) or HEMTs (high-electron-mobility transistor). In order to be able to achieve particularly high switching frequencies at low losses, it is expedient for the semiconductor switch elements to be formed from gallium nitride (GaN) or silicon carbide (SiC), that is to say a so-called wide-bandgap material.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.